Fuse



1933. N. M. STEPHENSON 1,925,060

FUSE

Filed July 28, 1930 Mrfnan J fiiephenson a, mum

Patented Aug. 29, 1933 UNITED STATES PATENT OFFICE FUSE Norman M. Stephenson, Los Angeles, Calif.

Application 'July 28, 1930. Serial No. 471,119

20 Claims.

The invention relates generally to electric fuses and more particularly to cartridge type of, fuses.

The general object of the invention is to provide a novel fuse which does not heat up to any great extent when carrying a current.

Another object is to provide such a fuse which opens the circuit, when the current exceeds the rated capacity of the fuse, without damaging the fuse.

A further object is to provide a fuse in which the gas generated by the blowing of the element is held to a minimum to prevent excessive pressure within the fuse.

Still another object is to provide a fuse having a novel form of element in which the portion blown is confined toa predetermined part of the element which is so shaped and so positioned relative to the rest of the element that only a small amount of metal is consumed.

2 A still further object is to provide such an element together with novel means to prevent detrimental arcing after the element has blown.

Another object is to provide an element having. anovel form together with means coacting therewith whichprevents any arcing in a straight line between the remaining portions of the element after it has blown.

A further object is to provide a fuse having a novel form of element in which practically no heat is generated in any part thereof except the portion to which the blowingis confined either under a normal operating current or under a blowing current.

Other objects and advantages will become apparent from the following description taken in connection with the accompanying drawing, in which:

Figure 1 is a longitudinal section of a fuse embodying the features of the invention.

Fig. 2 is' an elevation of a portion of the fuse shown in Fig. 1.

Fig. 3 is a perspective view of the fusible element used inthe fuse shown in Fig. 2.

Fig. 4is an elevation of a portion similar to that shown in Fig. 2 of a modified form of fuse.

Fig.5 is a perspective view of the fusible element used in the fuse shown in Fig. 4.

Fig. 6 is an elevation of a portion similar to that shown in Fig. 2 of another modified form of fuse.

'Fig. 7 is a perspective view of the fusible element used in the fuse shown in Fig. 6.

Fig. 8 is an elevation of a portion similar to that shown in Fig. 2 of another modified form Fig. 9 is a perspective View of the fusible element used in the fuse shown in Fig. 8.

While the invention is susceptible of various modifications and alternative constructions, I have shown in the drawing and will herein describe in detail the preferred embodiment, but it is to be understood that I do not thereby intend to limit the invention to the specfic form disclosed, but intend to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

The present embodiment of the invention comprises briefly a fusible element having an aperture therein, means for connecting the element in circuit, and an insulating barrier occupying the aperture in the element. For purposes of illustration, the invention is shown embodied in the knife-blade form of a fuse of the renewable cartridge type, but it is obvious that the invention may be embodied in the ferrule form of cartridge type fuses and in other types of fuses.

As shown in the drawing, the present embodiment comprises an insulating tubular shell 20 (see Fig. 1) and a pair of knife-blade terminal members 21 secured to the respective ends of the shell 20 by any suitable means. The particular securing means illustrated herein comprises a pair of ferrules 22 threaded internally into the respective ends of the shell 20 and having external threads on their outer ends.

In the left-hand end of the fuse shown in Fig. l, a washer 23 is secured to the terminal member 21, as by riveting a portion of the member 21 to the washer. The washer 23 has a diameter slightly greater than the internal diameter of the ferrule 22 and is arranged to be seated against a shoulder formed in the ferrule. To prevent relative rotation between the ferrule and the washer or terminal member 21, a pair of diametrically opposite lugs 24 are formed on the washer which are adapted to fit into corresponding notches in the ferrule 22. A cap 25 having an inturned flange abutting against the outer face of the Washer is threaded onto the ferrule to hold the washer 23, and hence the terminal member 21 in place.

On the right-hand end of the fuse shown in Fig. 1, a plain washer 30 is secured to the terminal member as by riveting. The washer 30 has a diameter slightly less than the internal diameter of the ferrules 22 or shell 20 so that it may be easily slipped longitudinally through the shell. Removably mounted on the terminal member 21 is a second washer 31 which is prevented from turning relative thereto by having a slot the shape of the knife-blade. The washer 31 is shaped similarly to the washer 23 and is secured to the ferrule in a similar manner.

Within the shell, each terminal member has an extension 32 preferably round and of substantial cross-sectional area so that it will have a negligible amount of electrical resistance. An axial aperture or pocket 33 is formed in the inner end of the extension 32 which is arranged to receive a lug 34 formed on an insulating member 35. The lugs 34 are of sufficient length so that when the caps 25 are screwed onto the ferrules 22, the extensions 32 abut against the ends of the lugs 34 to hold the insulating member 35 firmly in place.

Secured between the extensions 32 is a fusible element generally indicated at 40. While two such fusible elements are shown in Fig. 1, it is obvious that one or more such elements may be employed depending upon the amount of current for which the fuse is rated.

Each element is provided with a transversely extending portion 41 at each end having an arcuate notch 42 constructed to fit around the extension 32 and to be secured thereto between a pair of nuts 43 and 44 threaded onto the inner end of the extension 32. The inner nut 44 is preferably square to assist in alining the elements while the outer nut 43 is preferably hexagonal.

Each element 40 has an aperture therein, and an insulating barrier, which is a part of the insulating member 35, occupies the aperture in the element.

In the form of element shown in Figs. '1, 2 and 3, the element comprises a strip of metal of relatively great width so as to have but little electrical resistance. Formed on the opposite edges of the strip midway between the ends thereof are offset portions 45 and an aperture 46 is punched through the strip between the offset portions. The aperture 46 extends substantially across the full width of the strip to restrict the crosssectional area of the offset portions, thus causing the element toblow at the offset portions. The portions of the element extending from the offset portions to the extensions 32 having but little electrical resistance do not generate any appreciable amount of heat and hence do not cause the fuse to heat up when carrying a normal load.

Occupying the aperture 46 is aninsulating barrier 4'? which extends from the side of the insulating member 35 and'is a part thereof. When the element blows, the offset portions 45 are melted but the barrier 47 prevents any arcing in a straight line between the portions of the element adjacent the offset portions 45. Thus, only a relatively small amount of metal is reduced to a gas and no excessive pressures will be generated to damage the shell 20.

In the form of element shown in Figs. 4 and 5, only one offset portion 50 is formed on the side of the element, and the aperture is in the form of a notch 51 extending in from the side opposite to the offset portion 50. An insulating barrier 52 is of similar shape to the barrier 47 shown in Figs. 2 and 3, and cooperates with the element in a similar manner.

In the formof element shown in Figs. 6 and 7, a pair of offset portions 55 and a pair of notches 56 similar to those shown in Figs. 4 and 5 are formed on opposite sides of the element in a.

staggered relation to each other. Thus, a central portion 57 is formed which is joined to therest of the element only by the offset portions '55. Insulating barriers 58 are provided to fit within the notches 56 and to cooperate with the element in the same manner as described. When the offset portions 55 are blown, the central portion 57 is severed from the rest of the element to assist in preventing arcing.

In the form of element shown in Figs. 8 and 9. the element is formed of a relatively wide strip of metal in which a pair of alined and spaced notches 60 are cut in the opposite edges midway between the ends thereof. The inner end of one of the notches 60 is V-shaped while the inner end of the other notch is pointed to leave a V-shaped piece of metal 61 of restricted cross-sectional area connecting the parts of the strip on each side of the notches.

Cooperating with the element are a pair of insulating barriers 62 occupying the notches 60, the edges of the barriers fitting closely around the V-shaped piece 61 to prevent arcing between the parts of the strip on each side of the notches when the piece 61 is blown.

It is evident from the above description that I have provided a fuse having an element and means cooperating therewith which prevent detrimental arcing and excessive pressure when the fuse blows, as well as preventing the heating of the fuse to any great extent during the normal operation of the fuse.

I claim as my invention:

1. A fuse comprising, in combination, an insulating shell, terminal members secured at the respective ends thereof for connecting the fuse in circuit, a fusible element secured between said terminal members and having an aperture therein, and an insulating barrier occupying said aperture, said barrier extending substantially the full width of and blocking direct arcing between the main portions of said element on opposite sides of said aperture.

2. A fuse comprising, in combination, an insulating shell, terminal members secured at the respective ends thereof for connecting the fuse in circuit, a fusible element secured between said terminal members and having an aperture therein to confine the blowing of the element to the portion immediately adjacent said aperture, the portions of said element between said blowing portion and said terminal members being of relatively heavy metal to prevent the generation of heat therein, and an insulating barrier occupying said aperture and extending transversely across the full widthof said portionsto prevent arcing between said heavy portions of the element when the element blows.

3. A fuse comprising, in combination, a fusible element having an aperture therein and an offset portion of restricted cross-sectional area adjacent said aperture, means for connecting said element in circuit, and an insulating barrier occupying said aperture for preventing arcing between the parts of said element adjacent said offset portion when the element blows said barrier being extended transversely between the said parts of said element so as to block any direct arc therebetween.

4. A fuse comprising, in combination, a fusible element formed of a straight strip of metal with an offset portion on the side thereof and having an aperture extending across the strip to restrict the cross-sectional area of the offset portion, means for connecting the element in circuit, and an insulating barrier occupying said aperture to prevent arcing between the parts of the element adjacent the offset portion when the element blows said area therebetween, means for conne barrier being extended transversely between the said parts of said element so to block any direct arc therebetween.

'5. A fuse comprising, in combine elementiormed of a straight strip of in; a relatively-wide main portion. wi i tion on the side thereof and having an 2 is extending across the strip of substantially the width of said main portion to re trict "1e crosssectional area of the offset per ton, mean connecting the element in circuit, and an in" ing barrier of substantially the width of said portion occupying said aperture to prove in a straight line between the parts of the ma portion of the element when i blows.

' 6-. A fus'e'co'mprising, in combination, a fusible element formed of strip of me .tl having a main portion with a pair of offset portions on the respective sides thereofv in staggered relation to-each other and having a pair of notches extending in from opposite sides of the strip to ofiset portions to restrict the cross-sectional area thereof, means for connecting the element in circuit, and a-' pair of insulating barriers extending hrough the respective notches to prevent arcing between the parts of the main portion of the element when it blows.

' '7. A fuse comprising, in combination, a fusible clement formed of stripof metal having a pair of alined notches cut into the respective sides thereof, the inner end of one of said notches bein V-shaped and the inner end of the other no being correspondingly pointed to leave a V-shaped piece of the metal of restricted cross-sectional 1g the ment in circuit and an i suletlng be :ier extend-- ing into said notches and fitting closely around said V-shaped piece to prevent arcing when element blows.

8. A fuse comprising, in combination, an in-- sulating shell, a pair of terminal. members secured to the respective ends of l shell each member having an extension within the shell, a fusible element mounted within the shell, said elei ment being spaced inwardly a substantial distance to the respective ends of said shell, each member having an extension within the shell, and a fusible element mounted within the shell, said element being spaced inwardly a substantial dis the junctions of the extensions and their terminal members and having transversely bent ends with notches therein fitting around extensions, each extension having a pair of nuts threaded longitudinally thereon and clamping the transversely bent end of the element between each other.

10. A fuse comprising, in combination, an insulating shell, a pair of termi- "-1 members secured to the respective ends of d shell, each member having an extension wi hin the shell with a pocket in the inner end thereof, an insulating member supported between said ex--- tensions having a pair of lugs on respective ends extending into the pockets, and a fusible element having transversely bent ends, ex-- tension having a pair of nuts threaded thereon to clamp the transversely bent end of the eleinent between each other.

in a fuse, t combination of a pair of niina mbers each having an extension on the end ad nent metal having an ap' tore I transversely bent ends, each a pair of nuts tl eaded longitudinally thereon to clamp the transversely bent e; d of the element between other, one

' latlng member supported by said extensions between the adjacent ends thereof and having a bar *ier extending from the side thereof and py'lng the aperture in the element. 12. A fuse comprising in combination by to have a low sistance, means to connec' the element in circuit, said main portions having their ends directed toward each other beti portions, and said no tions being connected by a third portion of sai clement of materially restrict "l cross-sectional and of greater length. than the distance betwee main portions.

13. A fuse comprising in combination a fusible "ornied of a strip of metal having two main poi irons of substantial cross section whercby to have low resistance, means to connect the element in circuit, main portions having the. ends d rected toward each other and raced rt, 1' atingbarrier means interposed betwo said portions and extending transversely thereof to the opposite sides thereof whereby to prevent direct arcing between said portions, and said portions being connected by a tiird portion of said element of materially restricted crosssectional area of greater length than the distance between said main portions, said third portion and said main portions lying in a common plane.

14:. A iuse comprising in combination a fusible element formed of a strip of metal having two main portions of substantial cross section when by to have a low resistance, means to connect the element in circuit, said main portions having their ends directed toward each other and spaced apart, insulating barrier means interposed between said portions and extending transversel thereof to the opposite sides thereof whereby to prevent direct arcing between said portions, and

is l

of said element of materially restricted crosssectional and of greater length than distance between said main portions, said third portion having a part intermediate its ends offset tran rsely of the main portions with respect to its ends to avoid said barrier.

15. A fuse comprising in combination a fusible element formed of a strip of metal having two main portions of substantial cross section whereby to have a low resistance, means to connect the element in circuit, said main portions having the? directed toward each other and spaced ap t, insulating barrier means interposed between said portions and extending transversely thereof to the opposite sides thereof whereby to prevent direct arcing between said portions, and said portions being connected by a third portion of said element of materially restricted crosw sectional area and of greater length than the distance between said main portions, said third portion and said main portions lying in a common plane and having an intermediate part thereof offset in said plane to pass around the barrier means.

16. A fuse comprising in combination a fusible element formed of a strip of metal having two main portions of substantial cross section whereby to have a low resistance, means to connect the element in circuit, said main portions having their ends directed toward each other and spaced apart, insulating barrier means interposed between said portions and extending transversely thereof to the opposite sides thereof whereby to prevent direct arcing between said'portions, and said portions being connected by a third portion of said element of materially restricted crosssectional area and of greater length than the distance between said main portions, said main portions being of at least as large cross-sectional area adjacent the third portion as at any other part thereof.

17. A fuse comprising in combination a fusible element formed of a strip of metal having two main portions of substantial cross section where- '5 by to have a low resistance, means to connect the element in circuit, said main portions having their ends directed toward each other and spaced apart, insulating barrier means interposed between said portions and extending transversely thereof to the opposite sides thereof whereby to prevent direct arcing between said portions, and said portions being connected by a third portion of said element of materially restricted crosssectional area and of greater length than the distance between said main portions, said barrier being out of contact with said portions so as not to appreciably affect their heat and electrical conductivity characteristics.

18. A fuse comprising in combination an insulating shell, terminal members secured at the respective ends thereof and extending inwardly toward each other for connecting the fuse in circuit, a pair of oppositely disposed fuse elements connecting said members, said elements having their ends bent toward each other to engage said member and a barrier of insulating material interposed between the ends of said members and supported thereby to prevent direct arcing after the fuse blows.

19. A fuse comprising, in combination, a fusible element formed of a strip of metal having a main portion with a pair of ofiset portions on the respective sides thereof in staggered relation to each other and having a pair of notches extending in from opposite sides of the strip to the oifset portions to restrict the cross-sectional area thereof, and means for connecting the element in circuit.

20. A fuse comprising in combination a fusible element formed of a strip of metal having two main portions of substantial cross section whereby to have a relatively low resistance, means to connect the element in circuit, said main portions having their ends directed toward each other and spaced apart, insulating barrier means between said portions, and a third portion 0! materially restricted cross-sectional area connecting said portions, said barrier means being spaced from said third portion.

NORMAN M. STEPHENSON. 

